The present invention relates to a new and improved construction of automatically engageable jaw clutch.
The automatically engageable jaw clutch of the invention is of the type comprising a toothed drive hub, a toothed power take-off hub, and a clutch or coupling star axially displaceable with respect to the power take-off hub. This clutch star can be continuously connected with the drive hub for conjoint rotation by means of first teeth means formed thereat and has second teeth means which can be brought into engagement with the teeth of the power take-off hub by axially shifting the clutch star. Further, there is provided a screw socket or sleeve which is connected by a pair of coarse-pitch threading with the power take-off hub, only can be conjointly axially shifted or displaced with the clutch star but is however rotatable relative thereto and can be entrained by means of the clutch star by a pawl blocking device composed of a pawl and ratchet teeth when the drive hub overrides or overtakes the power take-off hub.
With a heretofore known jaw clutch or gear coupling of this type, as disclosed in Swiss Pat. No. 499,735, the teeth of the drive hub comprise straight teeth which are formed at the inside of a pot-shaped projection of the drive hub and continuously mesh with straight teeth formed at the outside of the clutch of coupling star. The power take-off hub is likewise pot-shaped in construction and possesses at its inside coarse-pitch threading which continuously engages with outer coarse-pitch threading of the screw socket or sleeve. The screw socket is axially displaceably guided upon a tubular-shaped projection of the power take-off hub and together with such delimits a cylindrical chamber or space. In the cylindrical chamber there prevails an oil pressure which strives to push the screw socket and together therewith the clutch or coupling star away from the power take-off hub. At the outside of the screw socket there is furthermore formed a pawl gear-tooth system or ratchet teeth operatively associated with pawls mounted at the inside of the clutch start. At the outside of each pawl there is arranged a pivot or tilt edge in such a manner that the centrifugal forces acting upon the pawls, during rotation of the clutch star, strive to bring the pawls into engagement with the pawl gear-tooth system or ratchet teeth. At the inside of the clutch star there are additionally formed helical teeth which come into engagement with helical teeth formed at the outside of the clutch hub when the clutch star is driven by the drive hub at such rotational speed that it strives to overtake or override the power take-off hub, whereby it entrains by means of the pawls the screw socket in the direction of rotation. Consequently, the screw socket is threaded into the power take-off hub, and, in turn, entrains the clutch star in axial direction with respect to the power take-off hub, whereby it overcomes the oil pressure prevailing in the aforementioned cylindrical chamber and displaces the oil contained therein, against the prevailing centrifugal force, into a further radial inwardly situated space or chamber. The same oil pressure ensures that the screw socket again will be screwed out of the power take-off hub, and thus, disconnects the clutch star from the power take-off hub as sooon as the rotational speed of the drive hub drops below that of the power take-off hub.
According to another known type of jaw clutch or gear coupling of the previously mentioned species, as disclosed in Swiss Pat. No. 390,007, the teeth of the drive hub and the power take-off hub are both straight external teeth and the clutch or coupling star accordingly possesses two straight inner teeth systems. Also in the clutch star there are mounted pawls which coact with a pawl gear-tooth system or ratchet teeth formed at the outside of the screw socket. The screw socket is provided at its inside with coarse-pitch threading which is engageable with coarse-pitch threading at the outside of a sleeve which is rigidly connected for rotation with the power take-off hub, but however axially displaceable in relation thereto. Radially within this sleeve there is arranged a piston rod of an hydraulic piston-and-cylinder unit which is connected with the clutch or coupling star. If, with this clutch, the clutch star overtakes the power take-off hub, and thus, entrains by means of the pawls the screw socket, so that such is threaded towards the power take-off hub, then there is only initiated the meshing engagement of the straight teeth of the clutch star and the power take-off shaft, and the clutch star entrains the piston rod of the piston-and-cylinder unit to such an extent until a control opening formed thereat communicates one side or face of the related piston with a pressure oil line or conduit. From this moment on the engagement of the jaw clutch is augmented by the oil pressure effective at the piston. In order to disengage the jaw clutch it is necessary to allow the oil pressure to be effective at the other side or face of the piston by actuating a valve.
With both of the heretofore known jaw clutches or gear couplings the coacting teeth of the clutch star and the power take-off hub are configured such that during complete engagement of these teeth the screw socket rotates forwardly through a small angle in relation to the clutch star so that the rotational moment transmitted by the drive hub to the power take-off hub does not load the pawls. The pawls are also, in the disengaged state of the aforementioned jaw clutches, completely relieved of load as long as the drive hub rotates slower than the power take-off hub. However, the pawls in the disengaged position always remain effective in a manner such that they only permit a forward rotation of the screw socket in relation to the clutch star. Each rearward rotatiion of the screw pocket in relation to the clutch start, on the other hand, has the unavoidable consequence that the pawls initiate the engagement operation in the described manner. Therefore, it is not possible to rearwardly rotate the power take-off hub in relation to the drive hub.
In the meantime it has been found that it is desired, in certain instances, to render possible a reverse rotation of the power take-off hub in relation to the drive hub. This, for instance, is the case with marine reversing gearing of the type described in my commonly assigned copending United States application Ser. No. 919,045 filed June 26, 1978 entitled "Marine Reversing Gearing" to which reference may be readily had and the disclosure of which is incorporated herein by reference. The marine reversing gearing of such application has a drive unit which selectively directly forwardly drives by means of a first clutch a pinion or rearwardly drives the pinion by means of reversing gearing and a second clutch.